1. Field of the Invention
The present invention relates to energetic and gas-generating compositions, and in particular to oxidizing compositions.
2. Description of the Related Art
There are numerous applications for gas-generating compositions. Energetic gas-generating compositions are commonly used, for example, in rocket propulsion systems as well as torpedos, safety air bags, etc. Oxygen-generating compositions also have utility in breathable air generators and underwater welding.
Of particular interest among these compositions are those which are liquids, in particular liquids which are oxidizers. Liquids are necessary for many propulsion systems since they can be pumped, and liquids are in general easier to handle and store than solids. The most commonly used liquid oxidizers for rocket propulsion have generally been liquid oxygen (LOX), inhibited red fuming nitric acid (IRFNA), hydrogen peroxide (H.sub.2 O.sub.2), aqueous hydroxylammonium perchlorate (HAP) and nitrogen tetroxide (NTO). Each of these liquid oxidizers has problems associated with use. For example, LOX requires cryogenic storage and is dangerous when spilled. IRFNA, NTO and H.sub.2 O.sub.2 also have handling and toxicity problems. HAP offers some advantages, but suffers from the presence of hydrochloric acid in the generated gas. Most of the liquid oxidizers in current use present a vapor toxicity or contact hazard, and are hypergolic, that is, spontaneously combusting, in the presence of fuels.
Thus, there are in fact a limited number of available choices of liquid oxidizers. That there is a need to fill the technology "gap" in liquid oxidizers of the contemporary art is seen, for example, in the following articles. In Mul, et al., Search For New Storable High Performance Propellants, (AIAA-88-3354, AIAA/ASME/SAE/ASEE 24th Joint Propulsion Conference, Boston, July 1988), the authors discuss the need for storable, non-cryogenic propellants with better performance properties. They discuss nitric acid, NTO and hydrazinium perchlorate as storable oxidizers.
Another problem with the available liquid oxidizers is that they are mostly limited to a single composition, and thus a single set of performance and physical properties. That is, they cannot be formulated to achieve different values of performance and physical parameters. Thus, variation of performance properties of propellant systems using these oxidizers can only be achieved by varying the composition of the fuel, thus limiting design options.
Anderson, W., et al., Low Cost Propulsion Using A High-Density, Storable, and Clean Propellant Combination, discuss the need for nontoxic, storable, restartable, throttleable and high density impluse systems for rocket motors. They suggest the use of high concentration hydrogen peroxide as a propellant. Although the authors describe hydrogen peroxide as nontoxic, direct human contact with hydrogen peroxide is extremely dangerous.
Rusek, J., New Decomposition Catalysts And Characterization Techniques For Rocket-Grade Hydrogen Peroxide, J. of Propulsion and Power, 1996, 12, 574-579, discusses the use of hydrogen peroxide as a rocket propellant, both as a monopropellant and as an oxidizer with hydrazine hydrate/methyl alcohol fuel.
Gas-generating systems in other applications also have problems associated with them. For example, chlorate-based "chlorate candle" oxygen generators are used for emergency breathable oxygen in some airplanes and in welding applications. Because of the solid nature of the sodium chlorate, many of these devices cannot be turned off once triggered, and the heat production from such a device can prove to be a fire hazard. A liquid-based oxygen generator might overcome this problem. Moreover, chlorate-based devices typically produce some byproduct chlorine, which is toxic, in the breathable gas, and do not produce any diluent for the generated oxygen.
Examples of liquid gas-generating and explosive compositions of the contemporary art are seen in the following U.S. Patents. U.S. Pat. No. 3,561,533, to McKinnell, entitled Controlled Chemical Heating Of A Well Using Aqueous Gas-In-Liquid Foams, describes a two-component hypergolic reaction system in which an aqueous foam of hydrazine or dimethylhydrazine and an aqueous foam of hydrogen peroxide are mixed. The system is used to heat oil wells.
U.S. Pat. No. 3,790,415, to Tomic, entitled Chemical Foaming And Sensitizing Of Water-Bearing Explosives With Hydrogen Peroxide, describes addition of hydrogen peroxide as a foaming agent/sensitizer to water-bearing explosives having ammonium nitrate and fuel. Here, the hydrogen peroxide is added to the thickened or emulsified explosive mixture, and decomposes in the formulation to provide oxygen bubbles for foaming before the mixture is detonated.
U.S. Pat. No. 4,047,988 to Weill et al., entitled Liquid Monopropellant Compositions, describes a monopropellant which is an aqueous solution of a secondary or tertiary amine, and an oxidizer such as perchloric or nitric acid. Hydrogen peroxide is also mentioned as a possible oxidizer. Here, the amine apparently serves as the fuel in the monopropellant. Properties of the compositions including low freezing temperature, and use as a torpedo propellant, are described.
U.S. Pat. No. 5,607,181, to Richardson et al., entitled Liquid-Fueled Inflator With A Porous Containment Device, describes an automotive airbag inflator using a liquid monopropellant composed of a hydroxylamine nitrate (HAN)/triethanolamine nitrate (TEAN)/water system. A system with hydrazine and hydrogen peroxide as liquid fuel components is also mentioned. HAN is a relatively expensive component, however. Moreover, TEAN serves as a fuel in this mixture, so the mixture probably cannot serve as a general oxidant for other fuels.
In addition to the above patents, U.S. Statutory Invention Registration No. H1,768, to Mueller et al., entitled Oxidizing Agent, describes liquid oxidizers comprising water, hydroxylammonium nitrate, and ammonium nitrate or hydrazine mononitrate. Two oxidizing agents designated OXSOL 1 and OXSOL 2 are described. Discussed applications include use in gas generators for air bags, rocket propellants and torpedo propellants.
A document entitled Advanced Chemical Propulsion Systems discusses the need to replace hydrazine as a fuel, and suggests use of HAN/TEAN in a catalytic thruster. As noted above, HAN is relatively expensive, and HAN/TEAN system probably cannot be used as a general oxidant with other fuels.
An additional examples of a possible utility of a gas-generating system is seen in Berezovsky, Pyrogen Fire Suppression System-Marine & Vehicle Applications, dated August 1997, which describes a fire extinguishing system (PyroGen) which is pyrotechnic-driven. The system produces an aerosol, and the composition of the system is not disclosed.
Based on my reading of the contemporary art, I have decided that what is needed is a gas-generating liquid composition which can be used as an oxidizer, and which has low cost, low toxicity and excellent handling properties.